1. Field of the Invention
The present invention generally relates to an apparatus for reproducing recorded data and a record format to record data, and more particularly to an apparatus for reproducing recorded data that reproduces a target track to be reproduced and an adjacent track by one beam, a crosstalk signal is generated, and the crosstalk is cancelled by deducting the crosstalk signal from a reproduction signal.
2. Description of the Related Art
To record data, various recording media have been provided such as a magnetic disk, a magnetic tape, an optical disc, and a magneto-optical disc. In order to record data on these recording media, a magnetic record mark is mainly used, since compared with semiconductor memory, data can be permanently stored at a low cost. Thus, apparatus using these recording media have been essentially needed to record information such as a graphic, image information or the like, for computers, at a present age in which much information is dealt with.
FIG. 1 is a diagram showing an example of a circuit configuration of a conventional data reproducing apparatus.
An optical head 11 reproduces a signal from a recording medium 10 such as an optical disk or a magneto-optical disc. In order to recognize an address at which information is recorded, an SUM/ID detector 19 detects address information from a SUM signal or a Wobble signal, and then an ODC (optical control circuit) 20 recognizes the address.
Moreover, a reference clock CLK is made from a PLL (Phase-Locked Loop) 18 synchronizing with a signal from a clock mark provided on the recording medium 10 for reproducing data. A signal process is conducted based on this reference clock CLK and then data is detected.
A reproduction signal from the optical head 11 is amplified by an amplifier 12, a high frequency noise is eliminated by a LPF (low pass filter) 13, and then the reproduction signal is supplied to an ADC (A/D converter) 14. A high-pass filter is not shown in FIG. 1 but is generally provided for low-pass fluctuation suppression and circuit saturation prevention. Alternatively, an analog equalizer may be used for waveform equalization.
The ADC 14 samples by a reference clock CLK supplied from the PLL 18. In a case in which data recording condition is different for each of data reproducing apparatuses, a phase of the reproduction signal may be shifted from that of the clock synchronized with the clock mark formed by the pre-pit. For this reason, the phase of the reference clock CLK (not shown in FIG. 1) may be adjusted.
An EQ (digital equalizer) 15 equalizes and forms a waveform based on a sample value sampled by the ADC 14. Then, the sample value is equalized into a PR (Partial Response) signal. The PR signal is detected by a ML (most-likelihood) detector 16 and then is decoded by a decoder 17.
Decoded data is sent to the ODC 20, and an ECC decode is carried out. An ECC (Error Correcting Code) check is conducted for the decoded data. FIG. 2 is a schematic diagram showing an example of a format. In FIG. 2, a simplified 2K ECC Block disk format of AS-MO (Advanced Storage-Magneto Optical Disk) Physical Specifications (Version1.0 April 1998) is shown.
Referring to FIG. 2, a header 21 is provided before data part 29 and either one of 2T-repeated data in which a bit string xe2x80x9c1100xe2x80x9d is formed, and 8T-repeated data in which a bit string xe2x80x9c1111111100000000xe2x80x9d is formed, is recorded. For example, an Auto Read Power Control Area 22 is to be used in order to measure amplitude of the 2T-repeated data and the amplitude of the 8T-repeated data and to adjust reproduction power. An Auto Gain Control Area 23 is used to adjust the amplification gain of a signal. A Read Clock Phase Control Area 24 is used to adjust the phase of the reference clock CLK made by PLL synchronization with the clock mark mentioned above, with the phase of the clock for sampling a data signal. A Buffer Area 25 is provided before the data part 29.
In such general formats including ISO specification or the like, a similar signal is also recorded on an adjoining track. Of course in the data part 29, unknown random data is recorded on the adjacent track.
However, there are problems described as follows in the conventional data reproducing method.
In order to improve an optical disk in high density, bit density and track density may be enlarged. As to improve in high density of bits, a technology such as a PRML (Partial Response Maximum Likelihood) technology using waveform interference is well known. However, if the track density is made high, cross-write and crosstalk occur.
The cross-write is a phenomenon in which when data is recorded on a track to be recorded by higher power than optimal power, the data is also recorded on an adjacent track of the track. The cross-write deletes information currently recorded on the adjacent track. Thus, an information signal quality of the adjacent track is deteriorated. A heat distribution on an optical disk is controlled by properly conducting strobe luminescence and power adjustment of a LD (Laser Diode), so as to avoid the cross-write. Crosstalk is a phenomenon in which the adjacent track signal intermixes in a beam spot when data is reproduced and a jitter is caused in the signal to be reproduced. Especially if the track density becomes higher, the crosstalk cannot be avoided.
The conventional technology (Japanese Laid-Open Patent Application No.58-121138, Japanese Laid-Open Patent Application No.5-205280) is known in which data recorded on the adjacent track is detected, the crosstalk signal is generated from the data, a crosstalk amount is measured, and then the crosstalk is canceled by deducting the crosstalk signal generated from a reproduction signal. In this conventional technology, the adjacent track signal is also simultaneously reproduced by three beams, and the crosstalk is canceled by adjusting and deducting gain. However, since three beams are needed in order to carry out simultaneous reproduction of the adjacent track signal in this conventional technology, it is difficult to adjust phase differences by distance differences among the three beams.
Moreover, in the conventional technology (Laid-Open Patent Application No.5-205280), a reproduction waveform by scanning two tracks including an adjacent track by one beam is sampled by an ADC (Analog to Digital Converter), and a sample value is stored in a storage area, beforehand. The sample value is used and the crosstalk is cancelled when data recorded on a target track is reproduced. However, the ADC, which converts one sample value into 6 bit (through 8 bit) data, is used. The huge storing area, that is, 6 bit (through 8 bit)xc3x97sample number (waveform length in which the crosstalk is cancelled)xc3x97two tracks, is needed as a storage area.
Furthermore, it is known that the pre-pit signal and the Wobble signal in an area to which address information is stored depend on a diameter of the beam spot. If track density is raised, the pre-pit signal or the Wobble signal is influenced by the adjacent track signal before an MO signal that read data information (such as user data) Consequently, crosstalk data cannot be reproduced. For this reason, in a conventional technology (Laid-Open Patent Application No.8-231139), a method of suppressing interference is proposed in that an adjacent pre-pit signal is shifted in a direction of arranging bits. However, in such a configuration, since an additional area is needed in the direction of arranging bits, a format effect becomes degraded. Even in such a configuration, when the track density is raised further, the crosstalk occurs. That is, in a case in which the track density is raised further, when the beam spot overflows a track, a signal for reproduction is superimposed with an adjacent track signal by the crosstalk. Then, the signal superimposed causes a jitter and a reproduction signal quality is degraded. Accordingly, an error rate of data is increased and the data cannot be reproduced correctly.
It is a general object of the present invention to provide an apparatus for reproducing recorded data in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide the apparatus for reproducing recorded data that generates a crosstalk signal by reproducing an adjacent track while simultaneously reading a target track and at least one adjacent track by one beam, and cancels the crosstalk by deducting the crosstalk signal from the reproduction signal.
The above object of the present invention is achieved by an apparatus for reproducing recorded data by decoding a reproduction signal read from the recorded data recorded on a recording medium in accordance with a predetermined algorithm, the apparatus including: a crosstalk signal generating part generating a crosstalk signal by converting adjacent data recorded on an adjacent track into a waveform of the reproduction signal; and a crosstalk signal eliminating part eliminating the crosstalk signal by deducting from the reproduction signal, wherein the reproduction signal in which the crosstalk signal is eliminated is decoded in accordance with the predetermined algorithm and reproduced.
In the apparatus for reproducing recorded data, it is possible to generate the crosstalk signal from the adjacent rack and eliminate the crosstalk signal, which is generated, from the reproduction signal from the target track to be reproduced.
Accordingly, it is possible to improve the quality of the reproduction signal from recorded data that is recorded on the recording medium where tracks are arranged at high density.
From a viewpoint of eliminating the crosstalk when data information (user data) is reproduced, the apparatus may further include a storing part having at least one memory and storing detected data detected by the predetermined algorithm when the recorded data is user data, wherein the crosstalk signal generating part generates the crosstalk signal by converting the detected data stored in the storing part into the waveform of the reproduction signal, and the reproduction signal showing the user data, in which the crosstalk signal is eliminated by the crosstalk signal eliminating part, is decoded by the predetermined algorithm and reproduced.
In the apparatus according to the present invention, since the detected data detected in accordance with the predetermined algorithm is stored and also the detected data is a bit value, it can be realized to eliminate the crosstalk by less storage area.
Conventionally, 6 bit (through 8 bit) sample data is stored. According to the present invention, only one bit is required to store. It is possible to realize by less storage area (xe2x85x9 through ⅙ storage area) than the conventional method. Moreover, since the crosstalk from the adjacent track only is considered by the off-track, it is possible to reduce the storage area to half area. Consequently, it is possible to reduce the storage amount greater than the conventional method ({fraction (1/16)} through {fraction (1/12)} the storage amount of the conventional method).
From a viewpoint of obtaining a precise crosstalk amount, the apparatus may further include a measurement data recording part recording a predetermined measurement data to measure a crosstalk amount; and an elimination ratio obtaining part obtaining the crosstalk amount based on the measurement data read from the recording medium and obtaining a crosstalk elimination ratio, wherein the crosstalk signal generated by the crosstalk signal generating part is eliminated from the reproduction signal based on the crosstalk elimination ratio.
In the apparatus according to the present invention, it is possible to obtain the precise crosstalk amount by reading the predetermined measurement data recorded on the recording medium. Also, it is possible to variably eliminate the crosstalk signal from the reproduction signal by the crosstalk elimination ratio.
From a viewpoint of realizing a media compatibility, the apparatus may further include a zero data storing part storing zero data only wherein the crosstalk signal generating part obtains the zero data from the zero data storing part when the crosstalk signal is not generated.
In the apparatus according to the present invention, the crosstalk signal is generated based on the zero data. As a result, the crosstalk signal is not generated. Therefore, it is possible to realize the media compatibility for a recording medium where data is recorded by another recording apparatus.
From a viewpoint of generating the crosstalk signal from the reproduction data, the apparatus may further include a read signal converting part converting decoded data into a read signal for reading the recorded data recorded on the recording medium, wherein the storing part stores the decoded data, the read signal converting part converts the decoded data stored by the storing part into the read signal, and the crosstalk signal generating part converts the read signal converted by the read signal converting part into the waveform of the reproduction signal.
In the apparatus according to the present invention, data decoded and output as reproduction data can be converted into the reproduction signal. Therefore, even in a case of using a code, such as a run length limited code, having a longer length after encoded than before encoded, it is possible to eliminate the crosstalk signal from the reproduction signal.
From a viewpoint of generating the crosstalk signal from data in which an error is corrected, the apparatus may further includes a read signal converting part converting corrected data into the read signal for reading the recorded data recorded on the recording medium, wherein the storing part converts the corrected data stored by the storing part into the read signal and the crosstalk signal generating part converts the read signal converted by the read signal converting part into the waveform of the regeneration signal.
In the apparatus, since the crosstalk signal is generated from data in which error is corrected, it is possible to eliminate a more precise crosstalk signal from the reproduction signal.
From a viewpoint of eliminating the crosstalk by reading two tracks, the apparatus may further includes a read controlling part controlling to read the recorded data recorded on a target track to be reproduced by an off-track, wherein the crosstalk signal eliminating part eliminates an actual crosstalk signal caused by the off-track from one side of an adjacent track, by deducting the crosstalk signal generated by the crosstalk signal generating part from the reproduction signal.
In the apparatus, since two track are simultaneously read by the off-track, it is possible to improve an accuracy of the reproduction signal by simply eliminating the crosstalk signal occurring from the adjacent track only.
From a viewpoint of eliminating the crosstalk by reading three tracks, the apparatus may further includes a target reproduction signal storing part storing the reproduction signal read from a target track to be reproduced, wherein: the storing part includes two memories and stores a previous detected data detected from a previous track of the target track and a next detected data detected from a next track of the target track; the crosstalk signal generating part generates a previous crosstalk signal and a next crosstalk signal based on the previous detected data and the next detected data; and the crosstalk signal eliminating part deducts the previous crosstalk signal and the next crosstalk signal from the reproduction signal stored in the target reproduction signal storing part.
In the apparatus, two crosstalk signals are generated from two adjacent tracks by reading three tracks. Therefore, it is possible to improve an accuracy of the reproduction signal more by eliminating the two crosstalk signals from the reproduction signal.
From a viewpoint of eliminating the crosstalk when the address information is reproduced, when the recorded data is address information, the crosstalk signal generating part generates the crosstalk signal by converting adjacent address information adjacent to the recorded data into the waveform of the reproduction signal, so that the reproduction signal showing the address information, in which the crosstalk signal is eliminated by the crosstalk signal eliminating part, is decoded in accordance with the predetermined algorithm to reproduce.
In the apparatus, it is not required to read the adjacent address information. It is possible to generate the crosstalk signal by converting into the waveform of the reproduction signal.
Therefore, without degrading the format effect in the address information area, it is possible to cancel the crosstalk of the address signal. Moreover, higher track density can be realized. Thus, it is possible to improve the recording density by an improved format effect.